Process for the isolation of cyclic saturated hydrocarbons from hydrocarbons by extractive distillation



United States Patent O 3,492,362 PROCESS FOR THE ISOLATION OF CYCLIC SATU- RATED HYDROCARBONS FROM HYDROCAR- BONS BY EXTRACTIVE DISTILLATION 3,492,362 Patented Jan. 27, 1970 SUMMARY OF THE INVENTION The present invention provides a process for recovering cyclic saturated hydrocarbons with 6 or 7 carbon atoms from hydrocarbon mixtures with a narrow boiling range Gottfried Nettesheim, Wesseling, near Cologne, Germany, 5 containing such hydrocarbons, which comprises hydroassignol' to Union Rheillihe Bl'allllkohlell-Kmftstoif genating any olefins and/or aromatic compounds present Aktiengqsellscfhgft, Wessellng, Cologne, Germany a in the mixture and isolating cyclic saturated hydrocarcorporafiqn firmany bons by extractive distillation, in the presence of an or- 12 r i F i gg g bggg k g ganic compound which is liquid or low-melting under noralms Pnor 989 U 12 3 mal conditions, consisting of an ester which is obtained Int CL C07c 3/00; i 3/34 by reacting phthalic acid, phosphoric acid or carbonic acid s 260 666 9 Cl i with a cyclic compound containing hydroxyl groups and/ or a lower chlorinated aliphatic alcohol, or a reaction product of ethylene glycol or its mononitrile with a phenol ABSTRACT OF THE DISCLOSURE 15 or aromatic alcohol. Isolation of cyclic saturated hydrocarbons containing 6 or 7 carbon atoms from narrow boiling range hydro- DETAILED DESCRIPTION OF INVENTION carbon mixtures containing said cyclic hydrocarbons by hydrogenating unsaturated components of said mixture F il f f g for s extractge a t of and extractively distilling with a solvent which is a liquid t e a i li f't Y foctar d CC 12g oltte invelnor low melting point organic compound and is an ester a ma easle; Pro an i obtained by reacting phthalic acid, phosphoric acid or cari g mlx i B 1 15 FY5 ifi flffi bonic acid with a cyclic compound containing a free hyz i g O i g 0 g i f e droxyl group or a lower chlorinated aliphatic alcohol or a fi i e y g I E fee 1.

product obtained by reacting ethylene glycol or its monoso a ere 1S or Se ec we y ogena 0 t nitrile with a Phen 01 or aromatic al 6 Oh 0L olefins, thus avoiding the losses of benzene by which th s would be accompanied. If the hydrogenated mixture is subjected to extractive distillation in accordance with the invention, it is possible to isolate not only the cyclohexane FIELD OF INVENTION formed from benzene by hydrogenation, but also the cyclohexane present in the mixture from the outset, which This invention relates to a process for the isolation of can, f" p make p 10% q fl total recoverable cyclic saturated hydrocarbons with 6 or 7 carbon atoms q y Y addltlon, the cyclohexane from a hydrocarbon i formed during the otherwise necessary hydrogenation of the olefins is also recovered. DESCRIPTION OF PRIOR ART Because they have relative volatilities of 1.9 and higher, it is of particular advantage to use, for example, benzyl It is known that pure cyclohexane, for example, can be phenyl phthalate, dibenzyl phthalate, 18-chloroethyl phthalisolated from hydrocarbon miXtuTeS colltainlng beIlZeHc, ate, tetrahydrofurfuryl phthalate, phenyl benzyl carbonate,

y lohexane, olefins and paraffins by initially hydrogenata diphenyl carbonate/phenylbenzyl carbonate mixture, di-

ing the olefins with selective catalysts. In this reaction, phenyl cresyl phosphate and diphenyl benzyl phosphate.

small quantities of the benzene are hydrogenated to give Benzyl phenyl phthalate and dibenzyl phthalate show the cyclohexane. High-purity benzene is then isolated by highest selectivity. The use of dibenzyl phthalate is also liquid-liquid extraction, extractive distillation with selecadvantageous because of its very limited tendency to crystive solvents or azeotropic distillation, and this benzene 1s tallise. Di henyl benzyl phosphate and diphenyl cresyl subsequently hydrogenated to give pure cyclohexane. phosphate, for example, are very suitable because of their It has been suggested to remove the parafiins and isolow viscosity and their thermal stability. It is also of adparaflins accompanying cyclohexane in hydrocarbon frac vantage to use ethylene glycol monophenyl ether or ,8-

tions by extractive distillation with phenol, furfurol, aniphenylmethoxypropionitrile because of their high relative line, cyclohexanol or dimethyl sulpholan. Due to the involatility,

adequate selectivity of these solvents, the cyclohexane ob- The following table compares some examples of contained in this Way is never more than 95 to 98% pure. Acventional solvents and solvents used in accordance with cordingly, it has to be recrystallised to increase the purity. the invention for extractive distillation:

TABLE Relative Critical solution temvolatility of perature 2,4-dimethyl pentane and Cyclohex- Iso-octane, M.P., cyclohexane ane, C. 0. Benzyl-phenyl-phthalate. 2.1 47 im. Liquid Dibenzyl-phthalate 2. 1 37 im. 40 Diethylene glycol monophenylether phthalate 2.0 im. 56 Di-B-chloroethyl phthalate 1.9 69 im. Liquid Tetrahydrofurfuryl phthalate 1.9 56 im. Liquid A mixture of diphenyl carbonate and phenyl-benzyl carbonate 2.0 3 82 Approx 30 Dibenzyl carbonate 1. 8 11 43 27 Bis-Z-ohloroethyl carbonate 1. 8 56 96 8. 5 Tri-B-ehloroethyl phosphate 2.0 im. im. Liquid Triphenyl phosphate 2. 0 50 Diphenylcresyl phosphate 1. 9 9 86 -38 Tricresyl phosphate poor in 0is0mers 1. 8 0 51 34 Diphenyl-benzyl phosphate 1.9 15 im. Liquid Triphenyl phosphate 3. 0 33 im. 50

TABLE-Continued Relative Critical solution temvolatility of perature 2,4-din1ethyl pentane and Gyclohex- Isopctane, M.P., cyclohexane ane, C. C. C.

2 parts by weight of triphenyl-phosphate-l-l part by weight of tri-flchloroethyl phosphate 2. 42 im. 40 fi-Phenylrnethoxypropionitrile 1. 9 65 im. Liquid 5-Phenylmethoxypropionitrile 1. 9 50 im. Liquid fi-(m-methylphenoxy)-propionitrile 1. 8 51 102 Liquid Ethylene glycol monophenyl ether. 2. 0 39 im. 2 Ethylene glycol mouobcuzyl ether. 1. 9 85 Liquid Ethylene glycol (libenzyl ether l. 8 0 31 Liquid a-chloropropylene-glycol y-phenylether 2. 0 91 Liquid For comparison:

Aniline 1 1. 4 80 Liquid FuriuroL. 1 l. 66 101 Liquid Phenol. l. 6 30 70 40. 9 Do 1. 35 30 70 40. 9

Relative volatility at 80% cording to Griswold et al., Ind.

im.:Immiscible.

To increase the efficiency of the fractionation, by reducing viscosity, it can be of advantage to carry out the extractive distillation at elevated pressure in order thus to be able to increase the temperature in the fractionating column. Y

Eng. Chem. 38, 67 (1946).

EXAMPLE 1 Diphenyl cresyl phosphate was used as the solvent. 5 kg./hour of a mixture of 15% of 2,4-dimethylpentane and 85% of cyclohexane were run into the top third Of a steam bafiie column containing 150 trays. 35 kgjhour of diphenyl cresyl phosphate were run in just beneath the uppermost tray at the appropriate tray temperature. The bottom temperature was 170 C. and the head temperature was 80 C. The reflux ratio was 8:1. The extract removed from the bottom product and the distillate had the following composition:

Extract Bottoms Distillate Cyclohexane, percent 99. Q5 10. 2 2, 4-dirnethyl pentane,

percent 0. 05 89. 8

EXAMPLE 2 5 kg./hour of a mixture of 15% of isooctane and 85% of methyl cyclohexane were run into the top third of a 150-tray steam baffle column. Diphenyl benzyl phosphate was run in just beneath the uppermost tray at a rate of 35 kg./hour. The reflux ratio was 8:1. The extract removed from the bottom product contained 0.1% of isooctane and the distillate contained 11.5% of methyl cyclohexane.

EXAMPLE 3 3 kg./hour of a mixture of 15% of n-hexane and 85% of methyl cyclopentane were run into the top third of a 125-tray steam baflie column. 25 kg./hour of dibenzyl phthalate were run in just beneath the uppermost tray at the appropriate tray temperature. The bottom temperature was approximately 160 C. and the head temperature was approximately 68 C. The reflux ratio was 8: 1.

It was not possible to detect any n-hexane in the bottom product, whilst the distillate contained 9.5% of methyl cycolpentane.

EXAMPLE 4 solvent for n-heptane/mcthylcyclohexane (ac- 30 kg./hour of the aforementioned solvent were run in just beneath the uppermost tray at the appropriate tray temperature. The bottom temperature was 170 C. and the head temperature was C. The reflux ratio was 17:1. The extract removed from the bottom product and the distillate had the following composition:

Percent Extract Bottoms Distillate Cyclohexane El 35. 0 2, 4-dimethylpentane/2, Z-dimethyl pentane. 0. 02 61. 2 2,2,3trlmethyl hut-ane 0.01 3.1 2, B-dimethyl pentune/ii-methyl hexane 0. 06 0. 7 Benzene 0. 01

EXAMPLE 5 1 lag/hour of a mixture of 15% of n-hexane and of methyl cyclopentane were run into the top third f a -tray steam baffie column. 12 kg. of B-phenlymethoxypropionitrile were run in just beneath the uppermost tray. The reflux ratio was 8:1.

The extract removed from the bottom product contained 0.1% of n-hexane, whilst the distillate contained 10.4% of methylcyclopentane.

What I claim is:

1. The process for the isolation of cyclic saturated hydrocrabons with 6 or 7 carbon atoms from hydrocarbon mixtures with a narrow boiling range containing such hydrocrabons, which comprises hydrogenating any olefins and aromatic compounds present in the hydrocarbon mixture and isolating the cyclic saturated hydrocarbons from this mixture as bottoms by extractive distillation, using as selective solvent an organic compound which is liquid or low-melting under normal conditions, consisting of an ester which is obtained by reacting phthalic acid, phosphoric acid or carbonic acid with a cyclic compound containing a free hydroxyl group or a lower chlorinated aliphatic alcohol, or a product which is obtained by reacting ethylene glycol or its mononitrile with a phenol or aromatic alcohol.

2. The process according to claim 1 wherein the extractive distillation is carried out at elevated pressure.

3. The process according to claim 1 wherein the solvent used in the extractive distillation is dibenzyl phthalate.

4. The process according to claim 1 wherein the solvent used in the extractive distillation is benzyl phenyl phthalate.

5. The process according to claim 1 wherein the solvent used in the extractive distillation is diphenyl benzyl phosphate.

6. The process according to claim 1 wherein the solvent used in the extractive distillation is diphenyl cresyl phosphate,

7. The process according to claim 1 wherein the solvent used in the extractive distillation is ethylene glycol monophenylether.

8. The process according to claim 1 wherein the solvent used in the extractive distillation is fl-phenylmethoxy propionitrile.

9. The process according to claim 1 wherein the solvent used in the extractive distillation is dibenzyl carbonate.

References Cited UNITED STATES PATENTS Jonach 260666 Tooke 20360 Cornell et a1. 20360 Merryfield et al. 260667 Hann 260-667 FOREIGN PATENTS Australia.

0 WILBUR L. BASCOMB, JR., Primary Examiner US. Cl. X.R. 

